An aspect of the invention relates to a method and a device to transmit data, for example, in a redundant computer system, in particular, in a high-availability system.
Usually, redundant concepts of automation systems or computer systems are distinguished according to media redundancy or system redundancy in terms of their availability and apportionment of redundant nodes. Media redundancy is understood as the redundant implementation of transmission units in order to increase the availability of the transmission units between two communicating data processing units. Media redundancy, in which one redundant node is provided for the medium and another redundant node for the transmitting station in each case, in a manner of comparatively tight redundant nodes, is used particularly in reliability-related automation systems or control systems of equipment where a failure of the data communication can lead to critical consequences in the equipment. Media-redundant systems are insensitive to effects on systems, which are connected to one another. One disadvantage of these media-redundant systems is that it is not possible to perform diagnostics with respect to a fault that may occur on the individual systems which are connected to one another, and even when it is possible to perform such diagnostics, it is possible only to a very limited degree. Accordingly, a system failure leads to a considerable reduction in the availability of the system and leads to considerable increase in the reaction times of the system.
In contrast, in the case of system redundancy in which only a single redundant node is provided to an entire system in a manner of comparatively wide redundant nodes, the availability of the entire computer system can be increased by making the reliability-related data processing units and other components, such as, decentralized controllers, printers, etc. redundant. Usually, the central control and safety-related input and output modules, in particular, are made redundant here. By such redundancy, which relates largely to the entire system, particularly high availability is provided, making it possible to provide targeted diagnostics for individual faults.
For media-redundant systems, usually so-called control gear is provided, which connect two-channel or multiply redundant data transmission from a single-channel control or data processing unit. Switching over or combining media redundancy and system redundancy is currently not possible.